<p>Celebrate 20 years of Harry Potter magic with four special editions of <i>Harry Potter and the Philosopher's Stone</i>.<br> <br> Gryffindor, Slytherin, Hufflepuff, Ravenclaw ... Twenty years ago these magical words and many more flowed from a young writer's pen, an orphan called Harry Potter was freed from the cupboard under the stairs - and a global phenomenon started. <i>Harry Potter and the Philosopher's Stone</i> has been read and loved by every new generation since. To mark the 20th anniversary of first publication, Bloomsbury is publishing four House Editions of J.K. Rowling's modern